question

buddhafragt avatar image
buddhafragt asked

MPPT charge current too low

I have a strange problem:
I have 2 MPPT 100/20 in parallel and a Venus/Rasperry firmware 2.94 with a DIYBMS via CANBUS.
If I have now switched on both MPPTs, MPPT1 has e.g. 300W, MPPT2 80W. If I switch MPPT1 off, MPPT2 has 380W.
But this is not always the case. After switching the MPPTs on and off a few times, it works again sporadically.
The maximum charging power is controlled by DVCC and is set to 40A, in the MPPT setup I see 20A in each MPPT. So there should be no power limitation.
It doesn't seem to be a defective MPPT either, I've already replaced it, the Firmware is the actual 1.61
Is this a Venus bug?

MPPT ControllersVenus OSRaspberry Pi
4 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
What voltage are your batteries?

What is the battery SOC?

What CCL is the BMS setting?

What power are your panels?

Is it winter or summer where you are?


0 Likes 0 ·
buddhafragt avatar image buddhafragt kevgermany ♦♦ commented ·
the battery is a 15c with 49.5V - 3.30V/cell, SOC 60%, at this Voltage the current is set to 40A. The panels have 3000W peak. We are in the tropics here, the sun is mostly the same.

I think it is not a setup problem, because after some times switching on and off the inverters and the Venus is it running correctly. But latest next morning the error occur again.


0 Likes 0 ·
Show more comments
3 Answers
buddhafragt avatar image
buddhafragt answered ·

I made some research and see in Node-Red the MPPTs report "1: Voltage or current limited", I would rather expect: "2: MPPT tracker active".

I dont know if it is important, in Victron Connect APP I see 20A max. charge current....

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·

20A is the charge current max (hence the name 100/20 - 100v PV max and 20A charging.)

How much PV do you have attached to each MPPT? What is your battery system voltage?

0 Likes 0 ·
buddhafragt avatar image
buddhafragt answered ·

bildschirmfoto-2024-02-10-um-124458.png

Sometimes it is OK again, in the chart you can see at 10:30 the charge seems to be limited to around 300W, then at 12:30 full power again...


bildschirmfoto-2024-02-10-um-124458.png (34.4 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image
kevgermany answered ·

There's a value, charge current limit (CCL). You see it in the battery monitor(I think) stats in VRM. Should be there in Node-red. Would be good to see that. If that isn't limiting things, perhaps there's an intermittent cable fault.

3 comments
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

buddhafragt avatar image buddhafragt commented ·

all seems OK.... can I monitor the max voltage the BMS is sending?

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ buddhafragt commented ·
Yes the CVL. Also sent by the battery.

There is a widget in VRM advanced for batteries.

On the GX itself under the battery in device list is the parameters and details is where you find information.


1 Like 1 ·
buddhafragt avatar image buddhafragt Alexandra ♦ commented ·
thank you, found it!



0 Likes 0 ·